Explosive-charge operated fastening tools



y 2, 1963 J. R. SIDDONS 3,095,573

EXPLOSIVE-CHARGE OPERATED FASTENING TOOLS I Filed Nov. 7, 1961 "/aazifz/zlzazi m 2a,

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JOHN ROYSTON SIDDONS ATTORNEYS United States Patent 3,095,573 EXPLOSIVE-CHARGEOOPIESRATED FASTENING T 0 John Royston Siddons, Lower Plenty, Victoria, Australia Filed Nov. 7, 1961, Ser. No. 150,828 Claims priority, application Great Britain Nov. 10, 1960 7 Claims. (Cl. 144.5)

This invention relates to explosive-charge operated fastening tools and it refers particularly to an explosivecharge operated fastening tool of the kind having a piston slidably mounted in it in such a manner that when an explosive charge is fired in the tool the piston moves linearly in a cylinder to project a fastening devicesuch as a pointed drive pin or a partly-screwed stud along a bore in a guide member into concrete, metal or other substantial solid material, the piston having a pusher which is of smaller diameter than the body of the piston and operates in the bore of the guide member to force the fastening device into the solid material. Such tools will hereinafter be referred to as fastening tools of the kind described.

. In fastening tools of the kind described and as at present constructed, the pusher is an integral or separately constructed extension of and moves as a part of the piston, and it is found that there is a tendency for the pusher to fracture after repeated use. It is an object of the invention to provide an improved construction in which this tendency is reduced or at least the expense of replacement is reduced. A further object is to reduce the usual loss of efiiciency or difiiculty of operation which results from excessive recoil or rebound of the tool. Another object is to provide a tool of the kind described wherein there will be less recoil of the tool when the explosive charge is fired, and which will operate in such manner that there will be a reduced tendency for the fastening devices to fish-hook, that is to say bend instead of properly penetrating the concrete or other solid material-particul arly when the fastenings are to be driven into densified concrete.

According to the invention a fastening tool of the kind described has a driving piston and a pusher constructed as separate parts with freedom for relative axial movement, the piston, when the parts are together, seating on the end of the pusher, or on an enlarged head provided thereon, and the piston having a throughway for gaseous pressure (resulting from the fixing of an explosive) leading from the cylinder to the seat for the end of the pusher.

Preferably the rear end portion of the pusher is received, as a piston, within a counter-bore in the piston and the seat is at the inner or rear end of the counter-bore. It is also preferred that the seat make a substantially gastight seal with the end of the pusher. There may also be a gas escape port, in the wall of the said counter-bore, which is opened or disclosed when the pusher moves away from the seat.

The said rear end portion of the pusher may be in the form of an enlarged cylindrical head, and the end of the head which seats on the driving piston may be chamfered.

A specific construction of a tool according to the invention will now be described by way of example, and with reference to the accompanying drawings, in which:

FIGURE 1 is a view of the assembly of driving piston, pusher, guide member and containing barrel, sectioned axially along a diameter,

FIGURE 2 is a side view of the driving piston,

FIGURE 3 is -a side view of the pusher,

FIGURE 4 is a side view of the guide cylinder,

FIGURE 5 is a side view of the containing barrel.

The explosive charge-operated fastening tool incor- 3,095,573 Patented July 2, 1963 porating this invention is of generally-conventional or known construction in that it has a barrel 10 having an exhaust port 30 and a breech plug 11 at one end for the reception of an explosive charge, a metal guide cylinder 14 mounted replaceably at the other end of the barrel, and a driving piston within the barrel. The guide cylinder 14 has an axial or central bore 16 for accommodation of a pin, screwed stud or other fastening device 15 which, as shown, has a pointed shank and a larger head or screwed part 15a.

In known constructions of tools of the kind described the driving piston 12 is made with a pusher extending forwardly thereof, so as to constitute a fixed part of the piston, the pusher being of such diameter as to be a sliding fit in the bore 16 and to be adapted to act upon the fastening device 15-when the piston is driven forwardly upon the firing of the explosive charge-so as to force the fastening device through the guide cylinder and into concrete, metal or other substantial solid material against which the front end of the guide cylinder is pressed prior to the firing of the explosive charge.

According to this invention, the driving piston 12 and the pusher 18 are made as separate parts having freedom of relative axial movement.

The driving piston 12 is of generally cylindrical shape, having flanges 19, 20 at its ends and :an intermediate flange 21. The rear end flange 19 has a circumferential groove 19a which accommodates a circlip 25' providing a relatively gas-tight seal between that end of the driving piston '12 and the internal wall of the barrel -10. A relatively small-diameter bore 22 extends along the central axis of the driving piston 12 from the rear end of the piston to a coaxial counter bore 23 in the front end of the piston. An exhaust port 24 is formed radially in the wall of the piston so as to communicate with the inner end of the counter bore 23.

The pusher 18 has a stem 28 which is a sliding fit in the bore 16 of the guide cylinder, at flanged head 27 at the rear end of the stem 28 and a neck 26 extending co-axially from the rear of the head 27, the neck 26 being a sliding fit in the countenbore 23 and having its rear end chamfered at 29. The length of the neck 26 is such that when its rear end is in contact with the shoulder 23a at the inner end of the counterbore 23 the rear surface of the flanged head 27 will be a small distance clear of the front end of the piston 12. When the rear end of the neck 26 is pressed against the shoulder 23a there is a substantially gas-tight seal between the two surfaces, but when the pusher 18 is moved forwardly a small amount relative to the piston 12 gas can escape through the bore 22 and exhaust port 24.

When the piston 12 and pusher 18 are in position prior to the firing of an explosive charge the rear end of the neck 26 seats on the shoulder 23a and the front end of stem 28 presses upon the fastening device 15, as illustrated in FIGURE 1. It is believed that when the explosive charge is fired the first effect of the explosion is to drive the pusher 18 forwardly relative to the driving piston 12, the pressure of the gases in the barrel 10 acting on the rear end of the neck 26 through the bore 22 in the piston 12. The pusher '18 thus acts on the fastening device 15 to force that device longitudinally of the guide cylinder and into contact with the concrete, metal or other substantial solid material into which it is to be driven. When the device 15 comes into contact with that solid material and experiences increased resistance the piston 12which is also driven forwardly by the explosive charge-follows up and provides a hammer blow on the pusher 18. Thus, it is believed, the shock of impact of the fastening device 15 with the solid material into which it is to be driven is followed immediately by the hammer blow of the piston 3 12 on the pusher. It is also believed that the shock of the hammer blow is reduced by the gas action between the rear end of the pusher 18 and the shoulder 23a at the bottom of the counterbore 23. l

I have found that when comparing a fastening tool having separate piston and pusher, according to my invention, with a similar fastening tool having a one-piece pistonpusher and using explosive charges of the same power, there appears to be less recoil With the fastening tool incorporating my invention, that the explosive charge can be increased in the fastening tool made according to my invention to provide for greater penetration of the fastening device into the solid material, that there appears to be less tendency for the fastening device to fish-hookthat is to say, to bend into somewhat J shape instead of straightly penetrating the concrete or other solid materialfor any power rating of the explosive charge, and that there appears to be less likelihood of breakage of the pusher. It is to be noted, with respect to the last feature, that even if the pusher does break, there is a lower replacement cost.

The barrel and other parts of the apparatus described above may be associated with a pistol grip type of handle incorporating a trigger and firing pin, or incorporated in a tool of the hammer or percussion operated types.

The exhaust port 24 may be omitted, but I have found that better results are obtained when the port is provided. Also the neck 26 may be formed with a circumferential groove to accommodate a circlip and thereby provide for a gas tight fitting of the neck 26 within the counterbore 23-.

The guide cylinder may be detached and replaced by another guide cylinder of different length if the length of the fastening device 15 be changed.

I claim:

1. In an explosive-charge operated fastening tool of the kind described a driving piston and a separate pusher,

the pusher being adapted to move axially relative to the driving piston and also being adapted to seat on the driving piston, and the driving piston having a through bore for gaseous pressure, whereby gas pressure resulting from the firing of an explosive charge in the fastening tool causes relative movement between the pusher and the driving piston.

2. A tool as claimed in claim 1 wherein the front end of the piston has a counterbore providing a seat at the inner end thereof for the rear end of the pusher.

3. A tool as claimed in claim 1 wherein said piston has in its wall an exhaust port that is normally closed when the pusher is seated on the piston and opened when the pusher is moved axially forward relative to the piston.

4. A tool as claimed in claim 1 wherein the pusher has an enlarged head near its rear end adapted to seat on the front end portion of the piston.

5. A tool as claimed in claim 1 wherein the piston has a sealing ring mounted in its external surface to provide a gas-tight seal between the external surface of the piston and the internal Wall of a barrel of the tool wherein the piston is mounted.

6. A tool as claimed in claim 5 wherein the pusher has a stern adapted to fit slidably in a guide cylinder of the tool, an enlarged head near its rear end, and a neck extending rearwardly of the enlarged head adapted to fit slidably in the said piston bore.

7. A tool as claimed in claim 5 wherein the piston has an exhaust port in its cylindrical wall communicating with the bore through the piston, the exhaust port being normally closed by the piston and opened when the pusher has moved a pre-set distance linearly forward relative to the piston.

No references cited. 

1. IN AN EXPLOSIVE-CHARGE OPERATED FASTENING TOOL OF THE KIND DESCRIBED A DRIVING PISTON AND A SEPARATE PUSHER, THE PUSHER BEING ADAPTED TO MOVE AXIALLY RELATIVE TO THE DRIVING PISTON AND ALSO BEING ADAPTED TO SEAT ON THE DRIV-RE ING PISTON, AND THE DRIVING PISTON HAVING A THROUGH BORE FOR GASEOUS PRESSURE, WHEREBY GAS PRESSURE RESULTING FROM THE FIRING OF AN EXPLOSIVE CHARGE IN THE FASTENING TOOL CAUSES RELATIVE MOVEMENT BETWEEN THE PUSHER AND THE DRIVING PISTON. 